No Sound :-(

Troubleshooting
1

After experimenting with playing sound from an external source on my Pokitto by playing audio into the audio_out pex pin, I now no longer have sound from my Pokitto itself :frowning:
Audio will still come out of the Pokitto through the audio out pin, but not the speaker. Which is more likely -

  1. Blown the speaker
    or
  2. killed the amp circuit?
2

Try if you get sound from headphone jack and report back

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3

Odd, it’s working again :-/ I didn’t do anything to fix it. It just started working again when I came back to it.

Looking at the diagram, would I assume that if sounds comes in through the pex audio pin, with would be amplified and then output through the speaker?

4

:open_mouth: comes in???

warning you are potentially doing something that will break if you are inputting a signal to that pin

1 Like
5

Hmmmm, it’s a pitty :frowning: the idea actually works :frowning:

…Would something as quiet as a line-out signal be damaging do you think?

6

Not unless you exceed the operating voltages - but i give no guaratees

1 Like
7

That’s just the encouragement I need :slight_smile:

2 Likes
8

Looking at the schematic, it appears that if you put a headphone plug into the Pokitto’s headphone jack, then you could safely feed an audio signal into the PEX pin. The plug could be connected to headphones or just be an empty, standalone one with all connections left open, since its purpose is only to open up the switch in the headphone jack.

Doing this, the audio would come out of the speaker. You wouldn’t be able to send audio from the PEX to headphones plugged into the jack. The volume of the audio coming out of the speaker would be strictly controlled by the amplitude of the of the PEX signal (which should not exceed 3.3V). This is because Pokitto’s on board volume control circuitry will not be in the signal path.

1 Like
9

You are 100% correct

10

Plugging in headphones passes the audio directly to the headphones and nothing out of the speaker. Also just jamming something in the jack to knock the switch results in no sound either.

I wonder if in the sound interrupt, if I just pass the input from an analog pin straight to the audio buffer would it produce a sound?

11

No sound from what source?

My suggestion to insert a plug into the headphone jack is only to allow safely playing sounds on the speaker from an external signal fed into the PEX “audio out” pin. It assumes that the circuitry is undamaged.

12

playing sound into the pex pin, with headphones plugged in plays the sound through the headphones and can’t hear anything on pokitto speaker. With cotton-swab plugged in, nothing through speaker.

13

hmmm, If I enable audio in mysettings.h, then I can no longer communicate with my i2c device :frowning:

14

If anyone wondering what exactly I’m intending with this experiment, here is a photo…

IMG_20200208_170651
IMG_20200208_1706511574×2179 718 KB

6 Likes
15

Is that a real radio connection???

16

It sure is, works quite well too! Other than the (potentially dangerous) speaker issue.

2 Likes
17

Dude, if you burn your Pokitto doing important stuff like that, a new board is on the house

Edit: is that a magazine article I see ? :wink:

1 Like
18

If the schematic for the audio circuit that @jonne published early in this topic is correct, then that shouldn’t be able to happen. Plugging in headphones should open the switch in the jack, which will disconnect the PEX “audio out” pin (and thus the speaker amp input) from the audio output and headphone circuitry. The PEX pin should then only be able to drive the speaker.

@jonne,
Does what @spinal said make any sense to you?

19

Not really. Its not behaviour that I am expecting. I will need to investigate myself how its even possible.

1 Like
20

@spinal did you enable the audio amplifier? it is disabled with a pull-down resistor (R47-2)
it’s connected to pin P1_17

DigitalOut amp(P1_17);
amp = 1;